1. Field of the Invention
This invention relates to an implantable, molecular electrophoretic pump for ionic drugs and, more specifically, it relates to a durable and improved pump which is adapted to supply, on a predetermined basis, desired quantities of medication.
2. Description of the Prior Art
It has been known that medicines may, in many instances, be employed more efficiently by providing a pump to deliver the medication to a patient at a more uniform rate than would be experienced by periodic injections through syringes. Such pumps have been provided with the capability of either being mounted externally of the body or implanted in the body. See generally Electronic Flow Rate Controller for Portable Insulin Infusion Pump by R. T. Ferguson et al., Diabetes Care, Vol. 3 No. 2, March-April 1980 pp. 332-337; A Totally Implantable Drug Infusion Device: Laboratory and Clinical Experience Using a Model With Single Flow Rate and New Design for Modulated Insulin and Infusion by Henry Buchwald et al., Diabetes Care, Vol. 3 No. 2, March-April 1980, pp. 351-358; Implantable Drug-Delivery Systems by Perry J. Blackshear pp. 66-73, Scientific American 241 (December 1979); and H. Buchwald, A Two-Phase Fluid Powered Insulin Infusion Pump with Basal/Bolus Capability Which Compensates for Pressure and Temperature Variability, Trans. Am. Soc. Artif. Internal Organs, 27, 263-40 (1981).
U.S. Pat. Nos. 3,894,538 and 4,140,122 disclose multichambered medicine supplying pumps which involve actual transfer of solution and require the use of moving parts.
U.S. Pat. No. 4,140,121 discloses an implantable dosing device which delivers drugs plus liquid and involves a variable volume medicine reservoir and a liquid chamber which is subjected to variations in volume through transport of liquid by electroosmosis.
One of the problems experienced with the prior art systems has been the need to use a system having movable parts, thus rendering the pump susceptible to breakdowns and also requiring large power consumption.
In spite of the foregoing teachings, there remains a need for a self-contained, refillable, externally programmable, implantable drug infusion device.